Anemia and granulocytopenia are major problems in burned humans. The causes of the anemia and granulocytopenia are unclear but there is little doubt that both contribute significantly to the morbidity and mortality in these patients. It appears that some of the decrease in red and white blood cells is due to increased destruction and loss of these elements through burned areas. It has also been suggested that there may be "burn toxins" which inhibit blood cell production. The object of the present study is to determine more precisely the exact nature of defects resulting in anemia and granulocytopenia in burned humans. These studies will employ the tissue culture techniques of granulocyte and erythroid colony formation in vitro. Studies will be carried out to determine the granulocyte and erythroid colony forming potential of bone marrow from burned patients and to determine whether inhibitors of granulocyte and red blood cell production exist in the serum of these patients. If such inhibitors can be shown to exist, they will be characterized as to their biochemical nature and method of action. Granulopoietic factors (colony stimulating factor) and erythropoietin will be measured in the serum and urine of these patients to determine whether exhaustion of these humoral regulators may be, in part, responsible as well. Finally, a preliminary study of the effect of hypertransfusion on hematopoiesis in burned humans will be undertaken. Patients studied during hypertransfusion will be compared with control patients for changes which occur in humoral regulatory factors, rates of hematopoiesis, white blood cell and platelet counts, erythropoietin and colony stimulating factor levels, incidence of infections, and time to recovery.